linux-kernel - Re: [PATCH] iio: trigger: sysfs: Disable irqs before calling iio_trigger

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Message-ID: <4871626.01MspNxQH7@n95hx1g2>
Date:   Mon, 3 Aug 2020 08:44:29 +0200
From:   Christian Eggers <ceggers@...i.de>
To:     Lars-Peter Clausen <lars@...afoo.de>
CC:     Jonathan Cameron <jic23@...nel.org>, <stable@...r.kernel.org>,
        "Hartmut Knaack" <knaack.h@....de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: trigger: sysfs: Disable irqs before calling iio_trigger_poll()

Hi Lars,

On Monday, 3 August 2020, 08:37:43 CEST, Lars-Peter Clausen wrote:
> The sysfs IIO trigger uses irq_work to schedule the iio_trigger_poll()
> and the promise of irq_work is that the callback will run in hard IRQ
> context. That's the whole point of it.
> 
> irq_work_run_list(), which shows up in your callgraph, has as
> BUG_ON(!irqs_disabled())[1], so we should never even get to calling
> iio_trigger_poll() if IRQs where not disabled at this point. That's the
> same condition that triggers the WARN_ON() in __handle_irq_event_percpu.
is my patch sufficient, or would you prefer a different solution?

> Are you using a non-upstream kernel? Maybe a RT kernel?
I use v5.4.<almost-latest>-rt

regards
Christian